Safety catheters are widely used and typically include a catheter hub with a catheter tube extending distally thereof to be placed intravenously, a needle hub or support with a needle cannula extending distally thereof to a sharp distal tip and extending through the catheter tube to expose the sharp tip in order to facilitate intravenous insertion of the catheter tube, and a tip protector through which at least a portion of the needle shaft passes and adapted to enclose or otherwise shield the tip of the needle cannula after it has been withdrawn from the catheter tube and into the tip protector.
One form of tip protector involves a clip that fits within the catheter hub. Such clips are readily recognized in that they are thin webs of metal or the like which are bent or otherwise formed to have a back wall and one or more distally extending walls, all generally of the same thickness. In a ready state of the clip, the needle shaft of the needle cannula passes through an aperture in the back wall of the clip and against the distally extending arm of the clip, and between the arms where there are two of them, to pass into the catheter tube in order to expose the sharp tip. The needle cannula may be pulled proximally so as to bring the sharp tip within the clip proximal of the distal end walls of the arm(s), whereupon the arms close down to block distal re-emergence of the sharp tip. Also, a protuberance or other feature of the needle shaft near the sharp tip is sized not to readily pass through the back wall aperture, such that the protuberance engages against the back wall. The sharp tip is thus considered protected by the clip, which may be thought of as the locked or fired position. Any further proximal movement of the needle cannula will pull the clip out from the catheter hub.
Portions of the clip may be urged radially outwardly into engagement with an internal feature of the catheter hub so as to secure the clip within the hub. In one form, the presence of the needle against an arm (and between two of them, if present) urges an aspect of the arm(s) radially outwardly into engagement with a rib or groove of the catheter hub. In that form of clip, when the needle tip is pulled into the clip in the fired position, closing down of the arms also causes the arm aspect to move radially inwardly and away from engagement with the catheter hub, thereby releasing the clip for easy removal from the catheter hub. That form of design may be thought of as a passive tip protector, in that the user need do little more to remove the clip from the catheter hub than pull the sharp tip into the clip. In another form, an aspect of the clip remains urged into engagement with the catheter hub even in the fired position, such that removal thereof requires application of a force to overcome the engagement, with the force being applied by tugging the needle cannula proximally to overcome the force. The latter type of design may be thought of as an active tip protector in that the user must apply the added tugging force to overcome the hold of the clip to the catheter hub in order to remove the clip.
Clips have a disadvantage in that they tend to scrape along the needle shaft as the needle cannula is pulled proximally from the ready position to the fired position. That scraping is objectionable and can be particularly problematic in the passive tip protector due to the forces involved in the needle shaft urging the arms radially outwardly into engagement with catheter hub. In the active tip protector, the forces involved between the clip arm(s) and the needle shaft can be lessened, but at the expense, in part, of requiring higher removal forces, which can be objectionable.
A couple of recent proposals have sought to separate the catheter hub engagement function of the clip from the clip protective function so as to obtain the benefit of easy removal provided by passive tip protectors with the reduced forces on the needle shaft provided by active tip protectors. Those proposals involve an outer member about the clip, with the outer member having an engagement portion held radially outwardly into engagement with the catheter hub feature by the clip in the ready position. In those proposals, a portion of the clip is adjacent the outer member engagement portion so as to limit the ability thereof to move radially inwardly and release engagement with the catheter hub. When the needle tip is brought into the clip to place the clip in the fired position, further proximal movement of the needle cannula pulls the clip proximally relative to the outer member to misalign the clip portion from the outer member engagement portion into a release position such that the engagement portion can move radially inwardly and out of engagement with the catheter hub. These proposals thus involve a clip as an inner member and an outer member thereabout, with the two being axially shiftable from the ready and fired positions to the release position.
Those proposals seemingly provide the benefits of reduced needle shaft and clip arm forces of the active tip protectors, with the ease of removal of the passive tip protectors. But they still have drawbacks and can benefit from improvements.